Apparatus for pulling tools into a wellbore

An apparatus for pulling tools down into a wellbore, said apparatus comprising:

• a. a shell structure forming the body of the pulling tool, said body having a first, downwardly directed end and a second, upwardly directed end;
• b. means connected to the shell for providing physical coupling to the tool;
• c. a mass slidably mounted in said shell for sliding movement along the longitudinal axis of said shell between first and second positions disposed nearer said first and second ends, respectively;
• d. electromagnetic means for sequentially propelling said mass to said second position at a first average rate of speed and returning the mass back to said second position at a second average rate of speed, said first average rate of speed exceeding said second rate of speed so that the net movement of the pulling apparatus is in the lower or downward direction because of reaction to the movement of said mass;
• and
• e. at least one fin structure mounted on the outside of said shell structure, said fin structure being designed to offer more resistance to movement of the pulling apparatus in one longitudinal direction than in the opposite direction.